Anions are increasingly recognized as problematic environmental contaminants. For example, excess nitrate in soil from over-fertilization has led to contamination in water sources worldwide. Nitrate run-off into water sources causes algal blooms—a process known as eutrophication—ultimately depriving water of oxygen and leading to dead zones in the world's lakes and oceans. Given the negative impact nitrate has on water sources, there has been considerable interest in the design and synthesis of receptors capable of sensing the molecule in solution. A number of studies have reported synthetic neutral receptors capable of binding nitrate in solution; however, most exhibit low affinity. Some reports have shown enhanced nitrate binding in polar solvents such as CHCl3 and even a few demonstrate high nitrate binding in more competitive solvents; however selectivity for nitrate remains rare.